Low Speed Pre Ignition (LSPI)?

Ockie

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#1
Hi guys. So last week I was driving up William Nicol going towards Hyde Park from Sandton Drive. Some of you might be familiar with that uphill. Anyway, I had the car in Sport mode as the climate control was on.

Anyway, I was going about 70kph (I think) and had my foot flat down and the car was pulling pretty well, but then I heard a loud "grrrr grrrrr grrr" or knocking sound coming from the engine. Immediately took foot off the accelerator, quickly turned climate control off and ECO mode on, downshifted and gave petrol and it was gone. I did not like that noise one little bit, so after some searching, I found something called Low Speed Pre Ignition. The Speed part of the name refers more to engine RPM rather than the kph speed the car is traveling at. It seems to fit what I experienced as my car has a small engine that is turbo charged. Also, it is a low revving engine so the engine speed is a bit lower than what I have found to be the case in other cars.

Do you guys think this was indeed LSPI that I experienced?
 

ghostim

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#3
Low-speed pre-ignition (LSPI), also known as stochastic pre-ignition (SPI),[1] is a pre-ignition event that occurs in gasoline vehicle engines when there is a premature ignition of the main fuel charge.[2] LSPI is most common in certain turbocharged direct-injection vehicles operating in low-speed and high-load driving conditions.[3]
LSPI events are random and infrequent, and their effects on impacted vehicles can include very high-pressure spikes, loud knocking noises and sometimes catastrophic engine damage.[4]
 

Ockie

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#5
You talking about knocking while lugging?
Well, it could not have been normal knocking I think because the car has 95 unleaded in it at the moment. Was not lugging it either as I try to make a point of being in the gear that the car wants and according to the gear indicator, the car was happy with being in 5 and was pulling nicely (though, it obviously was under load)
 

Ockie

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#6
What car? What engine? What rpm?
TATA Bolt 1.2 Turbo petrol

I did not pay specific attention to the RPM as I got a fright and was quickly switching of climate control and switching it to ECO mode and down shifting....but the Bolt in my opinion is a low revving engine.
 

Neuk_

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#7
TATA Bolt 1.2 Turbo petrol

I did not pay specific attention to the RPM as I got a fright and was quickly switching of climate control and switching it to ECO mode and down shifting....but the Bolt in my opinion is a low revving engine.
Take note of the engine rpm the next time it happens although I hope it doesn't. I travel that hill almost every day home from work and a high gear low rpm situation at full throttle in a small engine is far from ideal. I am not sure why you consider the Tata Bolt 1.2 T to be a low rpm engine, I have never driven one before but since it is turbo charged it is important to know when boost threshold is reached and try to limit going full throttle under this rpm when under heavy load.
 

Ockie

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#8
Take note of the engine rpm the next time it happens although I hope it doesn't. I travel that hill almost every day home from work and a high gear low rpm situation at full throttle in a small engine is far from ideal. I am not sure why you consider the Tata Bolt 1.2 T to be a low rpm engine, I have never driven one before but since it is turbo charged it is important to know when boost threshold is reached and try to limit going full throttle under this rpm when under heavy load.
I will check today what the RPM is at 70 or so kph. I consider it a low RPM engine because compared to other cars, specifically the Mini Cooper I had before had much higher RPM @ 120 compared to this one. This one is just below 3000RPM @ 120, while the Mini would 4000RPM at that speed. Well, one thing I can assure you of is that I wont be doing that again :)

https://mybroadband.co.za/forum/threads/your-rpm-120km-h.978625/
 

Neuk_

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#9
I will check today what the RPM is at 70 or so kph. I consider it a low RPM engine because compared to other cars, specifically the Mini Cooper I had before had much higher RPM @ 120 compared to this one. This one is just below 3000RPM @ 120, while the Mini would 4000RPM at that speed. Well, one thing I can assure you of is that I wont be doing that again :)

https://mybroadband.co.za/forum/threads/your-rpm-120km-h.978625/
3000rpm at 120km/h is perfectly normal from some of the petrol cars I have owned, both N/A and T, 4000rpm sounds too high to me and I can only imagine how noisy it must be.
 

Ockie

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#10
3000rpm at 120km/h is perfectly normal from some of the petrol cars I have owned, both N/A and T, 4000rpm sounds too high to me and I can only imagine how noisy it must be.
Okie dokie. Checked now and @ 70 it is about 1600rpm in 5th gear
 

Neuk_

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#11
Okie dokie. Checked now and @ 70 it is about 1600rpm in 5th gear
In that case, I would suspect LSPI as I doubt that boost threshold has been reached at that rpm, even on such a small engine/turbo.
 

crysis

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#12
Make sure you service regularly. Certain modern formula's of engine oil are designed to protect against LSPI. GM dexos1 Gen 2 oils are designed to limit this issue. Would be wise to make sure you are using such an oil, and that it gets changed regularly.
 

Ockie

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#13
Make sure you service regularly. Certain modern formula's of engine oil are designed to protect against LSPI. GM dexos1 Gen 2 oils are designed to limit this issue. Would be wise to make sure you are using such an oil, and that it gets changed regularly.
Car is booked in for service @ Tata for its 45k service this coming Saturday :)
 

Ockie

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#14
In that case, I would suspect LSPI as I doubt that boost threshold has been reached at that rpm, even on such a small engine/turbo.
Thank you Meneer. I will be sure not to put the engine into that operating condition again.
 

Neuk_

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#15
Make sure you service regularly. Certain modern formula's of engine oil are designed to protect against LSPI. GM dexos1 Gen 2 oils are designed to limit this issue. Would be wise to make sure you are using such an oil, and that it gets changed regularly.
How would the oil protect an engine against LSPI?
 

Ockie

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#17
How would the oil protect an engine against LSPI?
From what I read and understand....normal oil can vaporize and form small little droplets...and this is what actually starts vombusting prematurely and then cause lspi. The new oils designed to prevent it does not cause those little droplets inside the cylinders.
 
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